This artist rendering provided by NASA shows Voyager 1 at the edge of the solar system. NASA said Monday, Dec. 3, 2012 that the long-running spacecraft has entered a new region at the fringes of the solar system thought to be the last layer before the beginning of interstellar space, or the space between stars. Mission chief scientist Ed Stone says it's unknown when Voyager 1 will finally break through to interstellar space. Once that happens, it'll be the first manmade object to leave the solar system. (AP Photo/NASA)

This artist rendering provided by NASA shows Voyager 1 at the edge of the solar system. NASA said Monday, Dec. 3, 2012 that the long-running spacecraft has entered a new region at the fringes of the solar system thought to be the last layer before the beginning of interstellar space, or the space between stars. Mission chief scientist Ed Stone says it's unknown when Voyager 1 will finally break through to interstellar space. Once that happens, it'll be the first manmade object to leave the solar system. (AP Photo/NASA)